1. TECHNICAL FIELD
The present invention is related to a damaged conveyor belt detector with a mechanical linkage for sensing damage to a conveyor belt. More particularly, the invention relates to a damaged conveyor belt detector having an improved linkage mechanism which is suitable for use in an explosive environment.
2. PRIOR ART
Belt conveyors normally include a drive pulley and a take-up pulley that are operative to rotate an endless conveyor belt. Belt conveyors are able to move large quantities of many different types of materials efficiently. However, the conveyor belt is subject to wear and must periodically be replaced. While wear is unavoidable in most cases, belt life can be extended by repairing torn or damaged belts.
Conveyor belts may be torn or damaged in small localized areas by improper loading or partial unraveling of a conveyor belt splice. When a conveyor belt tears or is punctured the damaged portion generally hangs downwardly from the upper or lower run of the belt. These hanging portions are commonly referred to as trailers. Trailers frequently become snagged or wrapped about other parts of the conveyor or adjacent machinery. When this occurs, belt wear is aggravated and relatively minor tears or punctures can rapidly be enlarged until the entire belt is destroyed. Trailers also can cause damage to the conveyor structure, the operating mechanism or adjacent machinery. A badly damaged or completely broken belt can act like a giant whip which can destroy much of the conveyor structure.
If a torn or punctured belt is detected while it is still a minor localized tear, frequently the belt can be respliced, patched, or otherwise repaired to prolong the life of the conveyor belt. Repairing conveyor belts results in savings in both machine downtime and conveyor belt replacement costs because it is normally a simple matter to repair a small tear in a conveyor belt.
Various devices have been developed to detect the presence of tears or trailers on conveyor belts. One type of detector utilizes a rigid bar which is mounted below the conveyor belt to be impacted by a trailer. Upon impact the rigid bar trips a microswitch to indicate the existence of a torn section on the conveyor belt. Long trailers whipping under the belt may become entangled on the bar, resulting in increased damage to the conveyor belt. Rigid bar type trailer detectors are also subject to wear and may become bent after a period of use as a result of repeated impact by trailers. The trailer bar is mounted under the conveyor belt and its moving parts are continually subjected to debris and foreign matter falling from the surface of the belt. This dirt and debris increases wear on moving parts and limits the life of such a device.
Another type of damaged conveyor belt detector includes a cable anchored on one side of the conveyor and connected to a jack plug on the other side of the conveyor. The cable is mounted adjacent to the belt so that trailers, torn portions or objects that have punctured the belt will contact the cable and unplug the jack to switch a circuit. Such a cable is less subject to wear from repeated impact by torn belt sections and foreign material, but the jack plug may be damaged if it becomes entangled with a trailer. The jack plug is also subject to wear with repeated use because the prong of the plug is oriented perpendicularly to the direction that a trailer pulls on the cable. In time, the repeated pulling of the jack plug out of the socket loosens the connection until it eventually becomes loose enough to vibrate out of its socket. When this occurs, the detector will either sound a false alarm or shut down the conveyor, requiring a conveyor repairman to needlessly waste time checking the conveyor belt for damage.
In addition, prior art conveyor belt detectors are not suitable for use in environments where explosion proof electrical equipment is required. The jack plugs or switches of prior art detectors may result in sparks or arcing that cannot be tolerated in explosive environments.
The present invention is directed to overcoming all of the above problems and achieving other advantages not realized in prior damaged conveyor belt detectors.